Weathered P-38
The P-38 looks that way due to it being completely un-restored, supposedly Major Bong blew an engine on a test flight, You can read the full story on the plane here –
http://www.nasm.si.edu/research/aero/aircraft/lockheed_p38.htm
If you are interested I visited the NASM musuems in spring and my pictures from the trip are here –
http://spike.cs.umass.edu/~pbinder/NASM/
Paul